1. Technical Field
The present invention relates to a developing roller, a manufacturing method thereof, a developing apparatus and an image forming apparatus.
2. Related Art
Image forming apparatus that adopt electrophotography, such as copiers and printers, form images of toner on paper and other recording media by a series of image forming processes including a charging process, an exposure process, a developing process, a transfer process and a fixing process.
For example, in a developing process, with a developing roller that carries toner brought into contact with a photosensitive member that carries an electrostatic latent image, charged toner is provided from the developing roller to the latent image to visualize the latent image as a toner image.
For example, a developing roller for single component development as described in JP-A-55-26526 has hitherto been known as a roller for providing (applying) powder such as toner.
The developing roller, however, is manufactured by blasting a cylindrical material, which will be the roller, so as to roughen the surface of the cylindrical material.
Therefore, there is a problem in that the deformation of the cylindrical material occurs because of the use of abrasive grains, resulting in low yield.
To solve this problem, a developing roller that is manufactured by roughening the surface of a cylindrical material by using a centerless grinder without blasting has been known (e.g. JP-A-8-328376).
However, because the grinding marks (unevenness) of this developing roller are formed along the rotation direction of the roller, if toner is to be charged by friction, a developer rolls along the rotational direction of the roller to thereby make small the frictional resistance due to unevenness.
As a result, the developing roller causes insufficient charging and fog to occur.
On the other hand, a developing roller has also been known that has a large number of first grooves disposed in parallel to each other and a large number of second grooves disposed in parallel to each other to cross the first grooves such that a large number of grid-shaped protrusion portions defined by the first and second grooves is formed.
Such a developing roller, however, has a problem in that since the cross section of the groove is U-shaped and the top surface of the protrusion portion is a smooth surface, insufficient charging, toner leakage from a cartridge, and light and shade unevenness in an image occur.